Detailed Explanation:
A run chart is the best tool to illustrate trends over time, as it displays changes in data across a specific period.
Option D: Run chart
A run chart shows data points plotted in chronological order, making it ideal for observing trends or patterns, such as increases or decreases in medication errors over time.
Option A: Scatter diagram
Scatter diagrams show the relationship between two variables but do not display changes over time.
Option B: Pie chart
Pie charts represent proportions within a single point in time, unsuitable for illustrating trends.
Option C: Histogram
Histograms show frequency distributions but do not effectively illustrate trends over time.
References:
Run charts are recommended for tracking data trends over time, as indicated in quality improvement tools covered in CPHQ materials.